For a saltwater harbor, I would not choose furniture based on looks alone. The salt, wind, spray, and constant moisture will find every weak fastener and every spot where water can sit. The most reliable choices are commercial-grade pieces made with 316 marine-grade stainless steel, powder-coated aluminum, high-density polyethylene, teak, or well-sealed concrete and stone. These materials can handle salt exposure much better than mild steel, untreated timber, or standard zinc-coated hardware.
If I were specifying furniture for a waterfront plaza or harbor promenade, I would look for benches and tables with welded or concealed stainless fasteners, drainage gaps, sloped seats, and raised feet so water does not pool around the base. Powder-coated aluminum is a great option for lightweight seating and tables, provided the coating is thick and the cut edges are sealed. HDPE is excellent for slats and benches because it does not rot, splinter, or absorb saltwater. Teak can work well too, but it needs proper oiling and should use stainless hardware.
Cushions and fabrics need equal attention. I would choose quick-dry, UV-resistant, mold-resistant outdoor fabrics and make cushions removable so they can be stored during storms or heavy spray. For planters and waste bins, powder-coated aluminum, HDPE, or sealed concrete are safer than painted mild steel. The little details matter most: stainless screws, drainage holes, open frames, and easy access for rinsing.
A practical maintenance routine also makes a big difference. A simple freshwater rinse every few weeks, plus regular inspection of joints and coatings, will keep harbor furniture looking good for years. So the short answer is to specify marine-grade metals, HDPE, teak, or sealed masonry, avoid trapped water, and insist on corrosion-resistant fasteners. That combination gives urban outdoor furniture a real chance near saltwater.